High-speed internet access system

ABSTRACT

An asymmetric network system manages bandwidth allocation and configuration of remote devices in a broadband network. A modular architecture of the system permits independent scalability of upstream and downstream capacity separately for each of the upstream and downstream physical paths. Allocation of downstream bandwidth to requesting devices is made according to bandwidth utilization by other devices, bandwidth demand by the requesting remote device, class or grade of service by the requesting remote device or bandwidth guaranteed to other remote devices.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 08/899,883,filed on Jul. 24, 1997, which is a continuation of provisionalapplication No. 60/022,644 filed Jul. 25, 1996 titled “High SpeedInternet Access System.” The subject matter of U.S. Appl. No. 60/022,644is expressly incorporated herein by reference.

This application is also related to U.S. Pat. No. 5,586,121 titled“Asymmetric Hybrid Access System”, which issued on Dec. 17, 1996, andU.S. Pat. No. 5,347,304 titled “Remote Link Adapter for use in TVBroadcast Data Transmission System”, which issued on Sep. 13, 1994 inthe name of Eduardo J. Moura and James C. Long, for which re-issueapplication Ser. No. 08/340,733 was filed on Nov. 16, 1994. U.S. Pat.Nos. 5,586,121 and 5,347,304 are expressly incorporated herein byreference.

FIELD OF THE INVENTION

This invention pertains to a network management system that manages orcontrols data flow in an asymmetric network in which multiple usersshare a common broadband medium that conveys high speed data. Moreparticularly, this invention is directed to a network management systemfor managing bandwidth and controlling configuration parameters,including those affecting channel assignment, bandwidth allocation,transmit power setting, address assignment and the like in an asymmetricnetwork communication system.

BACKGROUND OF THE INVENTION

Medium access control provided by the present invention differs fromcontention-based and token-ring schemes in that a centralized networkmanager or controller regulates utilization of bandwidth by multipleremote devices connected to a shared medium rather than permitting theremote devices themselves to take control over the medium without priorauthorization. Further, the present invention differs from asymmetricnetworks that are provided by dedicated ADSL networks in that multipleremote devices share a medium.

The invention has application to CATV broadband networks, wirelessnetworks including cellular and satellite broadcast systems, televisionbroadcast systems, hybrid/fiber coaxial networks, cable communicationsystems, and telephony systems in which at least a portion of thecommunication paths between communicating nodes is asymmetric. Nodes ofthe network include servers, host computers, network devices andappliances, RF and cable modems and computing devices. In particular,the invention is directed to methods, architectural structures, systemsand components thereof useful for providing, facilitating and managingasymmetric communication using various switching or routing protocols,including ATM switching and IP routing, at various layers including thephysical, link and network layers.

A primary objective of the present invention is to provide anarchitectural structure, control system and method for allocatingbandwidth in an asymmetric network system.

Another objective of the present invention is to provide a method andsystem useful in an asymmetric network for managing configuration ofremote devices.

A further objective of the present invention is to provide methods andsystems for obtaining maximum bandwidth utilization by apportioningavailable bandwidth among multiple remote devices in an asymmetricnetwork utilizing a shared medium.

A further objective of the present invention is to provide anarchitecture which permits independent scalability of upstream anddownstream capacity in an asymmetric network system.

A further objective of the present invention is to provide a packetbased control scheme for managing with a configuration of remote devicesin an asymmetric network vacation system.

It is yet another objective of the present invention to provide thoroughpacket based control flexibility in assigning configuration parametersand bandwidth utilization through provision of a downloadable networkoperating software from a network management center to multiple remotedevices.

It is yet a further objective of the present invention to providemethods and systems for collecting usage data and statistical operatingparameters of the network which are subsequently used for bandwidthmanagement and configuration control of remote devices.

It is yet a further object of of the present invention to providemethods and systems for altering transmit level, frequency or time slotchannel assignments, global and local address assignments, account IDassignments and other properties of remote devices connected to a sharedmedium in asymmetric network.

It is yet a further object of the present invention to provide amanagement system which provides account administration for remotedevices connected thereto.

SUMMARY OF THE INVENTION

In accordance with the invention, an asymmetric network managementsystem, remote device or method involves the use of at least onedownstream channel carried in a broadband transmission medium and atleast one upstream channel operating in the same or different medium ata different speed or under a different protocol. The invention enables ahost computer to transfer information with a plurality of remote devicesover a shared broadband medium. A modular architecture of the networkmanagement system permits independent scalability of upstream anddownstream capacity separately for each of the upstream and downstreamphysical paths, and a network manager in the system managesconfiguration parameters of the downstream bandwidth allocated to remotedevices. The network manger effects allocation of downstream bandwidthto requesting devices according to bandwidth utilization by otherdevices, bandwidth demand by the requesting remote device, class orgrade of service by the requesting remote device or bandwidth guaranteedto other remote devices. Configuration parameters remotely managed bythe network manager include device addresses (global and local),transmission credit values, upstream channel assignments, upstreamtransmit power levels.

An additional aspect of the invention includes management ofconfiguration and bandwidth through control and response packetsgenerated at the network operations center and the remote devices,respectively. Control packets include poll packets that request, amongother things, upstream transmission requests. Configuration packetsinstruct remote devices to assume an operational state, return status orstatistical data. Response packets transmitted by the remote devicesprovide information to the network operation center for control purposesor to confirm their state of operation. Information packets are alsosent in both directions. IP or ATM encapsulation, as well as forwarderror correction and encryption, are employed. The invention hasapplication in broadband networks including RR, satellite and cablemedia, including those with telephony or router return paths.

These and other aspects, advantages and benefits of the invention willbecome more readily apparent in light of the succeeding disclosure andaccompanying drawings. The invention, though, is pointed out withparticularity by the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a layout of a preferred architectural structure of theinvention including an independently operating network manager, upstreamcontroller and downstream controller.

FIG. 2 is a functional block diagram of operational components of theupstream and downstream controllers in a cable-return asymmetric networksystem.

FIG. 3 is a functional block diagram of operational components ofupstream and downstream controllers for a telephony-return asymmetricnetwork system.

FIG. 4A illustrates the transmitter and receiver components of multipleremote devices in communication with respective transmitters andreceivers of a two-way cable system.

FIG. 4B is a depiction of the state machine illustrating generation ofupstream data and DONE packets transmitted by the remote devices.

FIG. 4C depicts a state diagram of remote devices in a transmit powerlevel setting scheme.

FIG. 4D shows a packet structure of a downstream data link frameencoding scheme.

FIG. 4E depicts a Reed-Solomon encoded packet structure.

FIG. 4F illustrates interleaving applied in a forward error correctionscheme on the downstream channel.

FIG. 4G. illustrates the packet structure of upstream frame transmittedby remote devices.

FIGS. 4H and 4I depict constraints of Viterbi encoding used in upstreamtransmission from remote devices.

FIG. 5 illustrates the sequence of remote device initialization andconfiguration.

SUMMARY OF THE INVENTION

An asymmetric network is defined as a network communication system inwhich at least a portion of the respective upstream and downstream pathsthereof operate at different speeds or under different protocols at thelink or network layer to enable a host or server to communicate withremote users or client devices. The disclosed embodiments are describedrelative to a client-service network that permits high speed dataservices over cable, e.g., a hybrid fiber coaxial cable network of aCATV system, but the teachings herein have equal applicability towireless data services including over-the-air TV and cellular broadcastsand direct broadcast satellite (“DBS”) networks. The definition ofasymmetry encompasses two-way wireless and cable systems having diversechannels or sub-channels, as well as telephone return cable andtelephone return DBS systems. Conventionally, data is transmitted infixed or variable length packets, but other data structures may beemployed. Because only a small percentage of existing cable networkssupport two-way data transmissions, the present invention also providescurrent CATV networks with a return by public switched telephonenetworks (POTS or ISDN) or by router.

FIG. 1 shows a network management system (i.e., a hybrid access system)that uses an asymmetric high-speed broadband network to provide dataservices over cable. The system provides end users, includingresidences, small businesses and schools with high-speed network-to-user(downstream) connections coupled with lower speed user-to-network(upstream) connections. Such configuration allows users to take fulladvantage of a modern, two-way, hybrid fiber/coaxial (HFC) cable TVinfrastructure and/or an existing telephone infrastructure. Theasymmetric communication system provides a complete transport solutionthat allows NSP's to deliver to their customers high-speed access to theInternet, online services, telecommuting services or any other TCP/IP orATM based application. The system provides an overall throughput of 30Mbps for each 6 MHz TV channel in the downstream direction and operatesfrom 128 Kbps to 2.048 Mbps in the upstream direction. The data ratesspecified herein obviously depend upon available bandwidth of operation.

The disclosed network management system provides a structuralarchitecture and pathing configuration that permits independent scalingof capacity on the upstream and downstream physical, link or networklayer. This allows a network service provider full control of cable dataservices that flow through the broadband network. A network operationcenter located at a centralized plant (i.e., a cable TV head end plant)controls configuration of remote devices; IP address assignments;upstream data rates; remote device power level settings and frequencyassignments; user traffic management and load balancing; subscriberaccount management; routing or switching management; bandwidthmanagement; and developing usage and performance statistics formodifying parameters that control such functions. The system also allowsconnections to other support and high speed networks.

The system uses standard CATV equipment such as television modulators,encoders, demodulators and channel processors for managing the upstreamand downstream data channels. Signals upconverted by the downstreamcontroller are mixed with other channels and transmitted to remote usersvia cable, first to the headend, and then to the remote users. Forwarderror correction techniques are employed in the transmission of signalsto ensure that data integrity is maintained over a range of cablesystems with varying quality. The head end equipment shifts thedownstream channel frequency to the cable channel frequency that hasbeen chosen for service by the remote sites. The head end also mixes todownstream signal with TV channels in the roll-off portion of thespectrum on the outgoing fiber link. The fiber cable carries the signalto neighborhood communities or businesses where they are converted to acoaxial cable signal. A conventional television cable splitter is usedat the terminal and to provide access for television entertainmentservices as well as data services to one more PCs.

Independent Scalabililty

The head end components of the network include a POP LAN switch 10 thatprovides intercommunication services for a downstream controller 12, andupstream controller 14 and a network controller 16. Modularity ofcomponents and independent upstream and downstream controller providesscalability of the respective upstream and downstream channels at thenetwork, link and physical layers. Providing independently operatingdownstream and upstream controllers 14 and 12, for example, facilitatesmatching equipment of a given capacity with desired traffic loadsindependently in each direction of an asymmetric broadband network. Inthe preferred physical arrangement, separate hardware racks or separatedrack-mounted components are used to establish independent operation andcontrol of the respective asymmetric paths. Each controller has its ownoperating system and either may be serviced without affecting theoperations of the other. Separation may also be achieved by partitionedoperation routines in a network operating system which controlrespective groups of upstream and downstream interface cards that handleasymmetric traffic.

Downstream bandwidth can be added independently from upstream bandwidthwithout affecting the other, and vice versa, simply by modifying orenhancing one of the components. Above all, the network managementsystem is optimized for heavy download and constant bit rate traffictransfers—including digital video, data and voice—by the very nature ofits asymmetric architecture. The pop LAN switch 10 shares an industrystandard multi-gigabit backplane switching hub with interface modulesfor Ethernet (10BaseT), fast Ethernet (100BaseT), TCP/IP router, T-1CSU/DSU and ATM Sonet. The pop LAN switch 10 acts like a bridge toprovide a single high bandwidth Ethernet fabric that connects to allrouters, ATM switching networks, servers, controllers or other networkcomponents.

Downstream controller 12 conveys high-speed data via a broadbandcommunication signal that is supplied upconverter module 18, which inturn, supplies the communication signal to a hybrid fiber coaxial systemof cable TV head end 20. In the preferred structure, controller 12 is anIntel or Sun-based microprocessor that provides channel service throughrouting or switching of downstream traffic from a server (local orremote) to a remote user or device. The upconverter module 18 includesencoders and modulators for converting digital data from the downstreamcontroller 12 into a form suitable for transmission over the CATV orwireless network, as the case may be. Several modulation schemes may beemployed by upconverter module 18, as known in the art. In theembodiment constructed by the inventors, both QAM and VSB modulationtechniques have been used. Assignee has also employed a technique knownas VQM (vestigial quadrature modulation) which is a special form ofvestigial sideband modulation to place digital data in a standardtelevision signal without disturbing picture quality. This is describedin assignee's co-pending application Ser. No. 08/820,347 filed Mar. 12,1997 in the name of William C. Levan for Network System Using TV ChannelTV Data Transmission Scheme, which is expressly incorporated herein byreference.

Continuing to describe the downstream path, hybrid fiber coaxialinfrastructure of cable TV head end 20 supplies a television or otherbroadband signal to a client cable modem, such as remote device 22.Device 22 includes a detector and demodulator for detecting andthereafter converting the broadband signal into a digital data stream.It too is microprocessor-based and includes operating software forperforming a multitude of functions, including DES decryption, hereindescribed. Once the appropriate data is detected, device 22 utilizes anEthernet interface to connect with and supply data to a computing device24.

The path of upstream data emanating from PC 24 is returned to the hostor server either through the same cabling infrastructure of cable TVhead end 20, or alternatively, via a telephone link as illustrated bythe telephone return path in FIG. 1. In the case of cable return, thecable modem 22, through its API interface with data processor 24,develops return data signals at an assigned frequency that differs fromthe frequency of the broadband signal in the downstream path. Theupstream signal is then transferred over the same cabling infrastructureused for the downstream path. Thus, upstream and downstream signalsshare the same cable 25 that pass signals through the hybrid fibercoaxial network of cable TV head end 20. As known in the art, channelsplitters, CSUs and DSUs are employed in the cabling network to provideindependent upstream and downstream channels. A channel processor 28reconverts the analog RF signals from the cable modem 22 into a digitaldata stream, and supplies the same to the upstream controller 14.Channel processor 28 is designed to process multiple upstream channelsfrom multiple fiber nodes. Also, the upstream channels may have datarates that accommodate multiple types of service desired by the remoteuser 24, such as, text, graphics, voice, video, teleconferencing, orother type of service, transmitted at either constant or variable bitrates.

Once the upstream controller 14 receives the data from the channelprocessor, it routes or switches the same to the POP LAN switch 10 fortransfer to its intended destination. In the case of IP packets, POP LANswitch routes data packets according to destination addresses containedin the packet. In the case of ATM packets, virtual paths are establishedfor temporary connections between a source and destination. As indicatedearlier, the controller 14 and/or network manager 16 provides amultitude of functions relative to configuration, frequency andbandwidth management, etc., so some of the packets transmitted by theremote devices 22 of 24 may be directed to the controller 14 instead ofother devices in the network.

In the case of telephone return cable system, a telephone modem 26(which may reside as the existing telephone modem card in computingdevice 24) develops return data signals in accordance with conventionalmodem communication protocols, and conveys the same over telephone linesto a modem bank in the upstream controller 14. As disclosed inassignee's co-pending grandparent application Ser. No. 08/426,920 (nowU.S. Pat. No. 5,586,121), incorporated herein, the modem return path mayproceed directly to a host or server providing interactive two-waycommunication with the processor device 24.

Still referring to FIG. 1, POP LAN switch 10 couples an Internet router30 and local servers 32 residing at the cable TV head end or wirelessbroadcast facility. Router 30 provides connectivity to remote servers orother local or wide area networks. Network controller 16, in thepreferred embodiment, controls, monitors, and prioritizes data flowingto and from the PC 24. Communication occurring between the remotesubscribers and a host located at the head end facility or other siteoccurs via packets. Downstream data packets are sent to the remotedevices in the form of TCP, UDP or ICMP IP packets. These packets may beencapsulated to transmit them according to ATM or any other switching orrouting protocol. Packets sent to a remote device include a destinationMAC address, a broadcast address or a multicast address. They alsoinclude an IP source address, network address or any other globally orlocally assigned address.

Packet-Based Control and Reporting

Advantageously, bandwidth and configuration management is achievedthrough transfer of numerous parameters contained in control packetsthat originate from the network management system and/or responsepackets that originate from the remote devices. Since the networkmanagement system is functionally modular, such management may beimplemented by any one of the independent downstream controller 12,upstream controller 14 or the network controller 16. Packet-basedcontrol permits assignment and removal of upstream channels depending ontheir operability status, frequency assignments, grade of service orbandwidth assignment, authorization requests, account administration anda multitude of other functions described herein.

Moreover, channel usage and operability statistics are collected bycomponents of the system and reported to other components to effectuatebandwidth management and configuration control. For example, theupstream controller's DSP collects channel quality data that is used bya configuration manager to remove or reassign upstream channels. Remotedevices report their bandwidth demand requirements to the upstreamcontroller which is used by the network manager for assigning downstreambandwidth over a shared medium or channel. Surplus spectrum allocated toidle remote devices may be reallocated to active remote devicesrequiring more capacity. Channels having poor transfer quality may beremoved. Loads may be balanced between different physical media. Devicesmay be switched to a different link, network or transport layer.

Respective control words, flags or nibbles contained in the control andresponse packets enable the network management system to perform thesefunctions. Because network operating software in the remote devices maybe downloaded from the network management system, their, operation maybe altered by re-configuring control packets to vary control and sensingfunctions effected by the control and/or response packets. As evident,management and control by such packets provide substantial flexibilityin the management system. Appendices A through E describe various typesof control information contained in control and response packets and thefunctions they provide.

Header information in control packets originating at the networkmanagement system includes a destination MAC address, a source IPaddress, a destination IP address, an IP type field, a UDP source portand a UDP destination port (port 473 in the preferred embodiment). Datavalues for control parameters follow this header. The header of responsepackets from the remote devices additionally includes a source MACaddress. These packets have a variable format that consists of a fixedheader followed by a variable length data field made up of operationunits. In a conventional manner, the remote devices parse each commandcontained in a packet, and execute the commands that appear in thecontrol packet based on the value assigned to parameters according tonetwork operations software running in the remote device 22. The valueof variables or parameters contained in the control packets may effectassignment of an address (global or local), assignment or change of anupstream transmit frequency, a change transmit power level setting,switching to another channel, issuance of transmission credits, ATMswitching or pathing control or alteration of a polling status from onepriority to another. Effectuation of other network management options isself-evident from the parameters and corresponding explanation set forthin Appendices A through E.

In a conventional manner as known in the art, a microprocessor in theremote device 22 places the control or status information in a registeror memory location, and thereafter executes instructions of operatingsoftware in accordance with flag bits and information contained in theregister or memory location. In addition, statistical trafficinformation may be accumulated by any component of the networkoperations center or the remote device to facilitate the control andmanagement functions. Functions of the remote device 22 may also beperformed by or reside in the client processor 24. Functions of atelephone modem 26 and RF modem device 22 may be combined in the remoteclient processor 24.

In particular, Appendix A describes the various fields (or entries) in acredit packet and their respective control functions that originate atthe network management system (e.g., the upstream controller). A creditpacket is used to issue transmission credits to a remote deviceauthorizing it to transfer a given amount of information. The remotedevice, after transfer, responds with a DONE message (described later).In the preferred structure, upstream channel control is achieved by apolling mechanism through credit packets, CMD_CREDIT transmitted overthe broadband downstream channel. Each credit packet is addressed to aspecific remote device 22 (or 24) and contains a credit to transmit aspecific number of packets on a particular upstream channel.

There are two types of credits that can be received by a remote device,limited and unlimited. The limited credit packet contains a credit valueless than the maximum allowed credit (0xffff). An unlimited credit isgiven when a credit packet is received with a credit value of (0xffff).Certain values of certain parameters, as noted herein, provide statuscontrol or configuration control. As seen in the packet structuredefined by Appendix A, the length of a control and status parameter mayvary from a nibble, byte, single or double word (real or integer), orfrom one bit to about 80 or more bits. Certain address information orremote identification indicia is burned-in the remote device.

Appendix B identifies the various fields of a poll packet together withdescribing the respective control functions associated therewith. Pollpackets are used, among other things, for detecting the transfer requeststatus of remote devices. In operation, the network management systemissues a CMD_POLL packet instead of a CMD_CREDIT packet in somesituations. The CMD_POLL packet has the same format as the CMD_CREDITpacket. The remote device cannot distinguish between the two packetswith the exception of the type of response it is to make. The remotedevice treats the CMD_POLL packet as a CMD_CREDIT packet except that itwill return an RSP_POLL packet (to report status) instead of an RSP_DONEpacket (to report an information transfer and/or an amount of remaininginformation to transfer).

Appendix C specifies the respective fields or entries, and controlfunctions thereof, of a subscriber address configuration packet format.The subscriber address configuration packet, CMD_CONF, configures the IPaddress and dataDestMac address of the remote device 22 (or 24). Theremote device uses the IP address, “assigned IP,” to configure thedownstream MAC address. For example, if the decimal IP address is 128.9.0.32, the remote device converts each decimal field to a hexadecimalnumber to obtain the locally administered MAC address:0×02:00:80:09:00:20. A complete configuration message may be split intoseveral CMD_CONF packets.

Appendix D identifies respective fields and entries, and the respectivecontrol functions, of one type of response packet that is transmitted bythe remote device. As indicated earlier, only two types of upstreampackets may be transmitted by the remote device 22 or 24. This includessubscriber data packets and response packets. Subscriber data packetscan be TCP, UDP or ICMP IP packets. These packets may beATM-encapsulated and are sent to the data destination MAC addressspecified in the packet. On the other hand, response packets includeRSP_DONE and RSP_POLL packets which are solicited by the networkmanagement system. The remote device transmits upstream packets on anassigned channel. In particular, the remote device transmits a solicitedRSP_DONE packet of Appendix D whenever it receives a CMD_CREDIT packetwith the SEND_DONE flag set. The remote device also periodicallytransmits a solicited RSP_DONE packet of the type shown in appendix Dwhen it receives an unlimited credit. Remote devices do not encryptRSP_DONE packets.

The Poll Response Packet of Appendix E identifies the various fields inrespective control portions of a poll response packet which hasattributes similar to the packet described in Appendix D, explainedabove.

Network Management System

The downstream controller 12 (FIG. 2) routes packets downstream;collects, stores and forwards traffic statistics; manages downstreambandwidth; encapsulates packets in the data link layer envelope;scrambles the data; and adds forward error correction. Controller 12supports an integrated, internal 64 QAM modulator card 42 or an external64 QAM modulator. The QAM modulators provide encrypted data rates of the10 Mbps and occupies 2 MHz of bandwidth of a 6 MHz TV channel. The TVchannel may accommodate three 10 Mbps channels. Dividing the downstreambandwidth into multiple broadband channel advantageously increase noiseimmunity (i.e., each band is affected differently by noise) and providealternative paths should one sub-channel fail. In the preferredstructure, each downstream controller 12 is configured to support up tosix independent downstream channels. The number of channels, of course,is a matter of design choice. The downstream router 12 connects to thepop LAN switch 10 via a standard Ethernet 100 BaseT port 40.

The downstream controller encodes Ethernet packets from the POP LAN hub10 and produces a QAM-modulated broadband RF downstream signal suitablefor transmission over a cable network. The signal is then converted viaconverters 44 to, for example, one volt peak-to-peak baseband videosignals for supply to the broadcast amplifiers for transmission over aconventional CATV channel at the head end. The downstream data istypically selected from the spectrum spanning from 50 MHz to 800 MHz. Toavoid using an existing video channel, the channel used by the networkmanagement system may correspond to a channel number somewhere above thelast usable video channel on the cable network, where the carrier tonoise level is small enough to allow digital data transmission witherror correction.

A hybrid fiber/coaxial cable network 46 carries the baseband videosignals to the remote users via cabling infrastructure 46. At the remotesite 48 a demodulator 50 demodulates the downstream video signal andsupplies the same to a microprocessor 49 which reconstructs Ethernetpackets. These packets are fed into a client PC device 24 (FIG. 1) usinga standard Ethernet adapter. Based on the capabilities of the broadbandnetwork, outbound information from the user's PC travels back to the popLAN switch by way of the cable system or public switch telephonenetwork. In the upstream direction, a VSB modulator 50 modulates datafrom the client processor 24. Microprocessor 49 effects control ofVSB-modulated upstream data to send it back up the cablinginfrastructure on an assigned channel, or to a telephone modem via, forexample, an RS-232 port.

The remote device or cable modem 48, as indicated earlier, provides astandard 10BaseT Ethernet interface for a PC. This provides high-speeddata services to the broadband network. In the preferred embodiment,each client cable modem 48 supports up to 20 PCs or workstationsoperating on an Ethernet LAN. Because many cable systems currentlyoperating are limited, the cable modem 48 supports a return path by wayof cable, public switched telephone network or by router return. Toreceive high-speed data via the ethernet LAN, cable modem 48 is tuned toa particular downstream channel frequency or time slot which isspecified through software provided either in the modem 48 or theworkstation 24 (FIG. 1). In addition, the client cable modem devices 48are accessible to the POP router 52 and local content servers 54 by wayof the downstream controller 12. For bi-directional broadband networks,the client remote device 48 includes a processor that processes the dataand sends it through a separate upstream channel. The upstreamcontroller 14 dynamically specifies the upstream frequency or time slotto enable the PC device to transmit data at speeds of 128 Kbps to 2.048Mbps. For unidirectional cable systems, cable modem 48 provides upstreamdata via modem to a modem bank associated with the upstream controller12 (see FIG. 3).

Upstream controller 14 manages the selection of upstream channels andperforms medium access control (MAC) functions. In a cable returnsystem, QPSK or VSB modulation is used on the upstream channel. As shownin FIG. 2, upstream controller 14 couples the Ethernet LAN switch 10through a standard Ethernet 10BaseT or 100BaseT port for respectivechannels in the upstream path from the client cable modem 48. Theupstream controller 14 tunes each channel, modulates data, extractsEthernet packets and routes the data to external sources based on IPaddressed. To achieve modularity, the upstream controllers 14 areconfigured to handle a maximum of twenty-eight channels each. Eachchannel is software configurable to operate at data rates from 128 Kbpsto 2.04 a Mbps which is controlled by software selectable parameters.

The POP LAN switch 10 is an Ethernet/fast Ethernet switch that providesa single high bandwidth Ethernet fabric which connects all routers,servers, downstream controllers, upstream controllers and networkmanagers. The POP LAN switch 10 operates at the link layer, but may beconfigured to operate at the network layer as well. The POP routers 52provide a wide area network. (WAN) for interfacing the Internet clout 34and/or other service networks through standard interfaces, such asT1/T1, SW 56, ATM SONET, T3, ISDN PRI, etc. A variety of POP routers maybe used within the network management system depending on the bandwidthof the required connections and the network protocols to be supported.

FIG. 4A illustrates the remote interface devices 72 through 74 whichreceive high-speed data from transmitter 76 and transmit lower speeddata to receiver 78. The transmitter 76 and receiver 78 are located atthe network operator's head end plant. High-speed communication from acable, or wireless signal distribution plant are conveyed fromtransmitter 76 along a downstream channel 77 which comprises a hybridfiber coaxial cable. Subscriber terminal equipment includes respectivereceivers 72 a and 72 b in communication with the downstream channel 77for receiving high-speed transmissions. Channels 77 and 79 may comprisea wireless or satellite transmission medium. The subscriber devices alsoinclude transmitters 72 b and 74 b that are respectively coupled to theupstream channel 79 for transmitting lower speed return data to thenetwork operator's head end equipment. In the head end equipment, mediaaccess algorithms control the subscriber's transmissions on the upstreamchannel 79. Media access control achieved through a downstream grantmessage is known as a “credit” packet and upstream relinquished/requestmessages are known as “done” packets.

There are two forms of credit packet control messages, CMD_CREDITS andCMD_POLL. Responses to the CMD credits and the CMD poll messages includeRSP_DONE and RSP_POLL messages. The remote devices do not distinguishbetween these two forms of messages, but the network management systemdoes. CREDIT packets and DONE packets refer to either type. The cableoperator's network equipment assigns an IP address and the downstreamMAC address based on the IP address of the subscriber's remoteequipment. The aspect of the invention described here sets forth howsubscribers acquire addresses and how the hybrid access system changesthe addresses for existing subscribers. The subscriber's downstream MACaddress is programmable by software in the subscriber's equipment inresponse to a command from the network operators equipment.

FIG. 4B depicts a state machine describing the upstream datatransmission and DONE packet generation in the remote devices 72, 74.When the remote devices receive a credit packet with a limited amount ofcredit, they transmit data packets on specified upstream channels untilthey have either used up their credit value or have run out of packetsto send. Remote device 72, for example, would then send a signal torelinquish its channel by sending a RSP_DONE or an RSP_POLL packet thatwas solicited by the network management system. The remote device 72does not retain the channel while waiting for more packets to send. Itonly transmits those packets that are available to be sent withoutinterruption. Also, the remote device does not introduce dead time inthe upstream transmission, other than inter-packet gaps between the timeit receives a limited credit packet and the time it relinquishes achannel with a done packet. In the special case where the limited creditissued by the network management system has a value of zero, the remotedevice does not respond by transmitting data packets, but instead,responds only with the solicited RSP_DONE packet.

When the remote device is provided with an unlimited credit(“credit”=max=0xffff), it transmits a solicited done packet on thespecified upstream channel and then transmits data packets whenever theybecome available. If the credit packet does not have the SEND_DONE orSEND_RSP_POLL flag set, the remote device will not send a done packet.If the remote device sends an unsolicited done packet, networkoperator's equipment will process it in a normal fashion. Dead time onthe upstream channel is allowed when unlimited credit is given. After anunlimited credit packet is received the remote device needs no furthercredit packets to use the assigned channel. If another unlimited creditpacket arrives for the same channel, remote device sends out anothersolicited done packet in response and continues to use the assignedchannel. If a limited credit packet is received, the remote devicefinishes any packet in progress, uses a limited credit assigned, issuesa solicited done and stops transmitting on the channel. The remotedevice assigned with an unlimited credit sends periodic unsolicitedRSP_DONE packets at a “heartbeatRate” that is specified in the creditpacket. Depending on the options available in the remote device, creditscan be based on the number of packets that can be sent or the amount ofdata that can be sent. In either case the credit amount does not includethe done response packet itself.

The functions performed by the remote devices 72 and 74 include 1)initialization which involves pre-configuration of the remote devicewith start-up parameters to enable further configuration by the networkoperator's equipment with an IP address; 2) re-configuration whichincludes assignment of a new IP address by the network operatedequipment; 3) power ranging which establishes a proper transmit powerlevel for upstream channel transmissions; 4) adjusting frequency (ortime slot) which entails changing the upstream frequency (or time slot)by the network management system to optimized upstream reception; 5)transmitting data rate adjustment, which entails adjustment of theupstream data rate in response to control messages sent by the networkmanagement system; 6) commanding responses which include sending ofresponses by the remote devices in response control packets sent by thenetwork management system in order to provide status information; 7)packet transmission which involves sending of data packets from theremote devices under control of the network management system; and 8)packet reception which includes filtering of packets by the remotedevices on the upstream channel and passing selected packets which areaddressed to the subscriber's PC. The remote interface device 48includes a router functionality which may limit the incoming packetsfrom the downstream broadcast to those destined for the subscriber's PCdirectly connected to it. At the subscriber's remote site, up to 20 PCsmay be serviced by a single remote interface device 48. This number mayvary according to design constraints.

The remote interface devices 72 and 74 have respective globally uniqueIP addresses “assignedlp” which all are configured by the networkoperator's equipment and downstream MAC addresses “downMacAddr” that areseparate and apart from their upstream MAC address. The downstream MACaddress is locally administered and is automatically configured based onthe assigned IP address and/or account number. The account number“accountNum” is used by the network operator to initially configure thesubscriber. It is an 11-digit decimal number that is given to thesubscriber by the network operator at the time of initial subscriptionto high-speed data services. This account number may be a subset of afull account number used by the network provider. The subscriber'sterminal equipment also includes an upstream MAC address “upsrcMacAddr,”which is used for response messages RSP_DONE and RSP_POLL. An upstreamdestination MAC address, “dataDestMac,” identifies the destination ofthe user data packets. A user identification number, “userID,” isassigned to each terminal equipment unit by the manufacturer. Blocks ofunique identification numbers are available from assignee hereof toterminal equipment manufacturers. When connected to the asymmetricnetwork, the remote interface devices 72 and 74 automaticallycommunicate their respective user ID's to the network management system.

The upstream MAC address (“upsrcMacAddr”), downstream MAC address(“downMacAddr”) and destination addresses (“rspDestMac” and“dataDestMac”) may be altered by the network management system or by thesubscriber's equipment. The user ID or an upstream MAC address assignedby the equipment manufacturer is burned in a ROM located in the remotedevice or interface 72, 74.

The remote interface devices 72, 74 are controlled by three commandpackets sent by the network management equipment on the high-speeddownstream channel 77. The first two packets are polling packets,CMD_CREDIT (Appendix A) and CMD_POLL (Appendix B), and are used to pollthe remote devices 72,74 and assign credits for sending data packetsupstream. The third packet, CMD_CONF (Appendix C), configures the remotedevices 72,74 with an IP address and an upstream destination MAC addressfor data packets, “dataDestMac”. The CMD_CREDIT and CMD_POLL packetshave a flag bit, SEND_DONE and SEND_RSP_POLL that are used to force aresponse from the remote interface devices. The remote interface devices72, 74 have no response to the CMD_CONF message. The downstream commandpackets and information in the upstream response packets are used by thenetwork management system to communicate with the remote interfacedevices and to control them.

Channel Assignment and Re-Assignment

An upstream channel within assigned frequency can be in use by zero,one, or several users. A channel can be declared to be “dedicated” andwill never be assigned to more than one user at a time, or a channel canbe declared to be “shared” and may be assigned to several users at atime. A shared channel is offered to each of the users in turn for theirsending the defined amount of traffic according to an assigned creditvalue. The network management system may characterize a particularfrequency (or time slot) at any point in time as unusable, beingqualified for use, or available for use. The usability of an upstreamfrequency or time slot can be changed over time to interference or noisecaused by energy sources. The upstream router or controller 14 negatesthis interference by adjusting the power level at which the remotedevices transmit, and by performing background checks on a channel thatis not in use.

The network management system detects failures or degradation of thedownstream channel and/or loss of communication with a particular clientdevice over an upstream channel. Degradation is typically indicated byan unacceptable cyclic redundancy check (CRC) error rate reported by aremote device on a particular node in the cable system. If a standbydownstream interface has been provided, the downstream controller 12 andremote device 48 automatically switch to a standby channel. Datacorruption in the downstream channel is determined by monitoring the CRCerrors in the downstream packets. In the case of a connection orientedsession (TCP), packets with CRC errors are re-transmitted by request ofthe transport layer protocol. For connectionless sessions (UDP), packetshaving CRC errors are discarded.

Failure or degradation of an upstream channel is determined bymonitoring the bit error rate and signal levels received at the upstreamcontroller 14. The upstream controller 14 then reports statusinformation to the network manager 16. When a failure or unacceptabledegradation is detected, the upstream controller 14 moves the remotedevice 48 to another available channel frequency on the node. The badchannel is continually monitored for usability and a channel qualitydatabase generated and stored in the upstream controller 14. A detectedbad channel is periodically monitored and is reassigned when theupstream controller 14 determines that it passes a criteria forreception and signal level. The upstream channel monitoring andreassignment functions are preferably performed by the network manager16, but again, any of these functions may be performed by other networkcomponents.

Bandwidth Management

Downstream bandwidth may be partitioned into classes of services suchthat users or applications can be assured of a certain level ofthroughput. The network management system performs a function to balancechannel usage among multiple channels in the downstream path that willallow for reserving bandwidth for selected clients sessions.

Downstream controller 12 performs bandwidth management. The total amountof bandwidth allocated to guarantee traffic is determined from aconfiguration file stored in the network management system and can bemodified by the network operator. If the traffic on the network exceedsa limit set by the operator, the downstream controller 12 strives toreach the limit over time without disrupting ongoing user sessions.Guaranteed bandwidth reservation is provided through an applicationinterface from the network operator's side, or the subscriber's side,and factors including the amount of bandwidth requested and inactivitytime is utilized in reserving a given amount of bandwidth. Inactivitytime-out values are utilized by the downstream router to drop sessionsor users which appear to have dropped out. In the preferred structure,downstream controller 12 reserves bandwidth in increments of 1 Kb persecond. Examples of applications using guaranteed bandwidth includevideo conferencing, video streaming, CD services and broadcast/multicastadvertising services. The services may require a fixed or constant bitrate, or variable bit rate service.

The bandwidth management function also allows an external applicationrunning in the network management system to move clients from onedownstream channel to another. In order to implement the load balancingfunction, the network management system obtains channel utilization, theamount of bandwidth that is not dedicated for guaranteed bandwidthfunctions, the utilization of other sessions, the number of sessionshaving guaranteed bandwidth and/or the amount of bandwidth dedicated toparticular source/destination IP address pairs. The channels orsub-channels from which the remote device 48 is moved are controlled bythe network management system. To perform the task, downstreamcontroller 12 or other devices in the network management systemmaintains internal routing tables that track the operativecharacteristics of the downstream channels, utilization and/orassignment thereof to the respective remote devices. The previouslocation and default frequencies of the listening channels of remotedevices are also maintained, otherwise the management system may losethe ability to find a remote device. The default frequency is afrequency on which a remote device will operate after power off, orafter a lengthy time-out from a poll initiated by the upstreamcontroller. The management system is equipped with the control panel orinterface to commit the network operator to override any automatic loadbalancing function. Multiple load balancing domains may also beprovided, each having its own load balancing algorithm or rules.

A downstream channel monitor is also provided for collecting data. Thisallows the network operator, through user interface facilities, toinspect and observe consumed channel bandwidth by the remote devices. Asoftware interface of the network management system allows viewing ofbandwidth data as a function of time. This enables the operator toallocate the guaranteed bandwidth on any targeted channel or user. Thechannel monitor permits the operator to set aside the total amount ofbandwidth dedicated to the guaranteed bandwidth service and/or to move aremote device or user from one load balancing domain to another.

Upstream routing provides for the delivery of data from a subscriber'sremote device to the network operation center. Data, for example, may bedelivered over 100 kHz sub-band channels at a rate of up to one two-wayKbps. Each subscriber connects to one physical fiber node of the cableoperator's distribution system. One or more physical fiber nodes aredefined for administration purposes to be a logical fiber node. Upstreamchannels are allocated among subscribers in logical fiber nodes. Eachupstream channel is assigned to a particular frequency. This means thatonce a frequency is occupied by a remote device on one physical fibernode, this frequency becomes unavailable to remote devices from otherphysical fiber nodes if they belong to the same fiber node grouping.

A channel scheduler, e.g., a program module, is provided in the networkmanagement system for assigning users to unoccupied channels. This meansthat the remote device is assigned to a dedicated channel if the remotedevice is not entitled to such service. As the need for dedicatedchannels arise for other devices who have reserved services, thescheduler may move a remote device which is not entitled to thededicated service to a channel that is shared. The scheduler willattempt to balance the load of shared channels based on channel usagederived from DONE messages. Channels will be managed by short-termschedulers that continue to support non-responding units, dedicatedservice, shared service, etc., though scheduler decides, based on classof service (dedicated, shared, . . . ) where to initially assign a newclient device connecting to the network. The information on the defaultclass of service for the client device resides in a table stored in atleast one of the components of the network management system and isprovided to the upstream controller 14. The scheduler may, at liberty,assign client devices to a class of service higher than the ones towhich they are entitled if there are sufficient resources to do so. Thenetwork operator is also able to set the maximum number of users pershared channel.

Channels allocated to different types of service will be determined frominformation contained in a configuration file. This information may bemodified by the network operator through an interface provided by thenetwork management system. When the current serviced type assignment onthe upstream controller 14 is modified by the operator, the networkmanagement system strives to conform to the new assignment over timewithout disrupting other user sections. Non-responding units are parkedon channels which have been designated for such service. At most, oneuser is present on a channel that has been designated a dedicatedchannel. Shared serviced channels are used by, at most, “n” users where“n” is greater than one. “N” may be set by the network operator. A testchannel is also provided by the network management system and will notbe available to normal network devices.

A short-term scheduling function of the network management systemmonitors incoming ports of the upstream controller to assess channelquality. Channel quality is based on the noise floor level. The noisefloor is continuously computed by digital signal processors that areresponsible for the channel. It is based on a running average of fifteenconsecutive samples, taken in consecutive fifteen symbol times,according to design choices. The information may also be averaged over alonger period of time, if necessary, to achieve some higher level ofnoise floor management function. The network management system mayindicate trouble upon detection of excessive noise, or even a very lownoise floor. The network manager removes bad channels from a pool ofavailable channels automatically, or channels may be removed underoperator control. Channels that are automatically disabled are returnedto the pool of available channels by the network management system whenthe conditions that caused their disability disappears. Manuallydisabled channels require manual enabling.

The network manager system may also be provided with a roving short-termscheduler that continuously scans the spectrum which is not allocated toany remote device. The roving function moves from one frequency toanother to measure noise floor level. Samples are collected andperiodically the quality of unused channels are compared to the noisefloor on channels which are currently assigned to other upstream ports.Such information is utilized by the network management system toallocate ports to a cleaner portion of the spectrum. In a preferredstructure, the DSP which manages a particular channel reports off-centerfrequency deviations of, for example, 2.5 kHz, and reports the same tothe scheduler for corrective action.

An upstream channel monitor collects data on the upstream channel. Thisfunction allows the network operator to observe the quality of upstreamchannels as detected at upstream controller 14 and the networkmanagement system to more effectively manage bandwidth and channelassignments. The user interface, provided by the network managementsystem, enables the network operator to view, upstream channelcharacteristics as a function of time and frequency. Informationprovided includes noise floor, carrier level, signal quality, carrierfrequency, signal-to-noise ratio, channel occupancy and utilization,channel type (dedicated, shared . . . ), and transmit power levels.Signal quality is a count which reflects degradation due to distortion,reflection, echoes, etc. The higher counts indicate lower qualitychannel. This count reflects the speed with which the equalizer softwareconverges in the DSP. In addition, the channel monitor allows theoperator to designate the channel as a Viterbi snoop channel whichallows the operator to enable a Viterbi error count display. Otherinformation available subject to DSP support includes the noise, thepower and ingress counts.

The channel monitor enables the operator at the network operation centerto manually override power settings of any remote device. In addition,the network operator may manually disabled or enable channels, setalarms for unacceptable signal-to-noise ratio, Viterbi count errors tonoise floor level, frequency deviation and signal quality. Moreover, thenetwork operator may modify power operating ranges for a client device,the fiber node or group of fiber nodes, or the system generally.Further, the network management system enables the operator to modifythe type of channel usage, i.e., non-responding, dedicated, shared,test, or roving service for DSP configuration. The network operator mayalso download new software into the DSP or reconfigure the DSP.

Forward Error Correction

The downstream controller 12 packetizes, frames, bit-stuffs,Reed-Solomon encodes, and interleaves the downstream data as specifiedin FIGS. 4D and 4E. The remote devices 72,74 reverse the steps to decodeand extract the original data. Downstream data is sent over the cable ina downstream frame that encapsulates an Ethernet packet (FIG. 4D).Encapsulation is performed by the downstream controller 12 whichconstructs an Ethernet packet and prepends an Ethernet preamble of oneor more preamble bytes and one start byte thereby to construct theEthernet frame. Thereafter, the Ethernet frame is bit-stuffed byreplacing consecutive trains of fifteen ones with fifteen ones followedby one zero. The controller 12 marks the end of the Ethernet frame (EOF)with a flag comprising a unique pattern, e.g., one zero bit and sixteenone bits. The downstream frame is then transmitted on the downstreamchannel one at a time with the least significant bit (LSB) beingtransmitted first. The network equipment sends data continuously on thedownstream channel. If no packets are available to be sent the networkequipment sends an idle pattern. The downstream data link interface idlepattern byte is a repeating pattern (e.g. . . . 11001100 . . . ).

The serial bit stream containing downstream frames and inter-frame idlepatterns is scrambled using conventional algorithms. The output of thescrambled bit stream is encoded with a Reed-Solomon forward errorcorrection (FEC) algorithm. For every block of 228 bytes of data, 20bytes of forward error correction checksum symbols are added, asindicated in FIG. 4E. FIG. 4E depicts the constructed frame, thegenerator polynomial, and a primitive polynomial for Reed Solomonencoding. The downstream controller 12 of the network management systemforwards the bytes of the Reed-Solomon forward error correction blockleast significant first starting with the data byte, continuing throughto byte 228, and then starting with the least significant byte of the20-byte checksum.

After the forward error correction algorithm is applied to the data,bytes from the forward error correction blocks are interleaved.Interleaving takes eight bytes of data from each of 32 forward errorcorrection blocks to form a new serial stream, as indicated in FIG. 4F,which shows taking bytes 128 from block 1 followed by bytes one througheight form block 32, and so on, up to 128 bytes from block 32. Afterthis, bytes 9-16 are taken, blocks one through 32. This continues untilall 248 bytes from all 32 blocks are sent and is again start over withthe next 32 forward error correction blocks of data. An interleavedgroup is made up of 7936 bytes of data (32 channels×248 bytes/channel).For every interleaved group, a three byte-interleaved synk flag isadded. The flag is: 0x33, 0xa5, 0xe1. This flag is transmitted with0x33, least significant bit first.

Upstream Frame Format

FIG. 4G. depicts the upstream frame format for packets transmitted fromthe remote devices 72, 74 to the network operations center, e.g., theupstream controller 14. In operation, remote devices send Ethernet datapackets upstream in an encapsulated frame. Frames are sent in burst modewith no signal period (inter-frame time) between them. To begin atransmission, the remote device initiates a frame transmission with apreamble pattern of a specified number of symbols, but does not encodeor scramble the symbols. The Ethernet packet follows the preamble, theleast significant bit being transmitted first. The remote device thentransmits Ethernet compliant packets, byte by byte. An end of frame(EOF) sequence is also inserted. Thereafter, the packet isViterbi-encoded using a constraint length of seven symbols, as shown inFIGS. 4H and 4I.

Configuration Management

The network controller 16 is an SNMP (simple network managementprotocol) based network management system that is used as a networksystem administration interface for the downstream and upstreamcontrollers (routing or switching devices), as well as for other POPdevices. Controller 16 provides a GUI-based editor to perform networkconfiguration management and facilitate full definition and automaticdistribution of all network configuration files associated with therespective remote devices. It provides the POP system administrator withan easy-to-use facility to configure the system; to provision for newsubscribers and manage accounts; to monitor POP equipment; to manage anddiagnosed client cable modem devices; and to initiate correctiveactions. It also allows the direct and automatic configuration ofdatabases and networks for use with other routers and hosts. Networkcontroller 16 also acts as a bandwidth manager, traffic statisticscollector and IP address database, as well as performing many othertasks identified by the parameters of Appendices A through E. Some ofthese configuration tasks are further explained below, but all areself-evident from the control and information packets described in theappendices.

IP Address Management

The network management system described herein also provides efficientuse of rapidly dwindling IP addressing resources. Routing traffic todownstream channels allows network administrators to assign sub-addresspartitions from an IP address space allocated by InterNIC. The networkmanager 16 effects assignment of address partitions to each channelwhich fits the number of subscribers or remote device 48 located atsites remote from the network operations center of the cable head end.As the number of subscribers increases, network manage 16 expands thedownstream channel addressing by adding additional self-addressedpartitions. Downstream routing is sufficiently flexible so that networkcan adapt to any extended IP addressing standard that may be affected byInterNIC. Control of IP address management may be effected either by thenetwork controller 16 or the downstream controller 14.

Status Reporting

A microprocessor in the remote interface device 48 runs a simplemanagement network protocol which allows the network management systemto communicate directly with it for purposes of checking connectivitystatus, and diagnosing and troubleshooting network operations. Thenetwork operating software required for operations of the remoteinterface device 48 resides in the downstream controller 14 and/or thenetwork manager 16 which, when a new remote device is connected orupdated, is automatically downloaded from the network controller 16 ordownstream controller 14, depending on the configuration. The remotedevice 48 also includes simple management protocol software which isused to set up, communicate, and diagnose the remote device 48. Thesimple management protocol software is automatically distributed toremote device 48 by the network management system. Also, the networkmanagement system is provisioned to gather traffic statistics from theremote devices in order to implement load balancing and other trafficmanagement functions.

Upstream Data Rate Adjustment

The remote device may transmit data at rates that are selectable inincrements of 128 Kbps. Preferably, the maximum transmit rate of theremote device is determined at subscription time. The network operator'sequipment sends credit control packets with transmit rates, “data rate”,encoded in them according to the following table;

TABLE I Transmit “dataRate” Rate Encoding (kbs) Special Command or Notes0x00 0 Trans. Off, cease sending data or response packets 0x01 128 Basicdefault rate 0x02 256 0x03 384 0x04 512 . . . . . . 0x0c 1,536 0xff32,640

In response, the remote devices utilize the parameter “dataRate” forconfiguring itself to transmit at the commanded data rate.

Power Level Adjustment

The network management system may also altered to transmit power levelof the remote device 72, 74. In operation, the remote device searchesfor an appropriate level of power at which the network equipmentreceives or detects upstream data packets, or alternatively, thetransmiter level may be explicitly set by the network operator'sequipment. The usual procedure entails the remote device searching foran appropriate level until “heard” by the network equipment, and thenthe network equipment sets the power level. When the remote device 72receives a credit packet having a level value of zero for the powerlevel setting, it sets to transmit power at maximum attenuation. As aconsequence, done packets sent upstream will not be received by thenetwork equipment. The following table depicts a typical transmit powergain implemented in the upstream channel:

TABLE II “power” Gain 0x0 min. transmit level −1.25 dB/mv 0x1  +2.75dB/mv 0x2  +6.75 dB/mv 0x3 +10.75 dB/mv 0x4 +14.75 db/mv . . . . . . 0xf+58.75 db/mv

A remote device transmission level state machine is depicted in FIG. 4C.As illustrated, when a credit packet is received with a level value of“power”=0x1, the remote device enters a “searching” state and startstransmitting with the level set to +2.75 dB/mv. As seen, the remotedevice searches for the level that can be “heard” by the networkmanagement system, and stops the search and goes into the “fixed” statewhen it sees a credit packet with an explicit level power≠1. Any timethe remote device receives a credit packet with the level step 21, itgoes back into the “searching” state and re-starts the power levelsearch again while in the searching state. The remote device transmitsat least two responses at a level before incrementing to the next. Thenetwork equipment adjusts the power level of the remote device any timeby changing the level in a credit control packet. For dedicatedchannels, the credit packet is set with unlimited credit to changeremote device transmit power and not otherwise affect the channelassignment. The remote device waits for a unique packet that is in theprocess of being transmitted to finish before the power level ischanged.

Upstream Frequency Adjustment

The network management equipment automatically adjusts the remotedevice's transmit carrier frequency in increments of 1 kHz by way of a“ctlFreq” parameter transmitted in a credit control packet. The upstreamtransmit frequency may be altered at any time. For dedicated channels, acredit packet is set with an unlimited credit to change the remotedevice's frequency and otherwise not change the channel assignment. Theremote device waits for any packet that is in the process of beingtransmitted before changing its frequency. The following table depictshexadecimal values for the parameter “ctlFreq” and associated upstreamtransmit frequencies:

TABLE III 0x00000000 0.000 Mhz . . . . . . 0x00001388 5.000 Mhz0x00001339 5.001 Mhz 0x0000138a 5.002 Mhz . . . . . . 0x000fffff1,048.575 Mhz   

On initial power-up, the remote device sets its upstream transmitfrequency to 4 MHz until it has received a credit or polled packet fromthe network management system instructing a different frequency.Similarly, in the situation where upstream channels are defined by timeslots, channel adjustment is made by changing the slot(s) at which aremote device is assigned.

Configuration of Remote Device

FIG. 5 illustrates a sequence of operations used for connecting a newsubscriber to the network. In step 1, a subscriber acquires a cable andinstalls a hardware modem (e.g., remote device 48). Prior to installingthe software the network operator provides an account number to thesubscriber. The cable modem user interface device, during installation,prompts the subscriber for the account number. Thereafter, the softwareautomatically configures the downstream MAC address for the remoteinterface device 48. In the preferred operation, the network operatoralso provides the subscriber with the downstream channel to which theremote device shall be tuned or slotted. Configuration features in theremote device include a) variable data transmission rates which areavailable and parameters of the remote device to indicate the variousupstream data rates the subscriber's equipment desires and is able tooperate (the default data rate is 128 Kbps); b) a credit scale whichindicates the units of packets, e.g. data length, the remote interfaceis able to transmit (remote interface device supports packet basedcredits as a default or packet length-based credits as an option); andc) a transmitter carrier range wherein the network management equipmentissues credit to transmit at a particular frequency (or time slot) of anupstream channel. These optional features are detected by the networkequipment through flag option queries, credit packets and doneresponses.

In step two of FIG. 5, the subscriber has completed installation processand has powered on the remote device 72,74. At this point, the networkoperator's equipment begins polling with CMD_CREDIT or CMD_POLL packetsthat are addressed to temporary addresses programed into the downstreamMAC address, “downMacAddr.” At this stage, the network equipment uses anarbitrary number for the assigned IP address. Although CMD_POLL packetsare transmitted to the remote devices 72 and 74, they do not distinguishbetween the command types. The network management system will sendinstructions during the initial poll with the power level setting set atthe lowest level 0x01 and no credit granted. The network managementequipment requests the remote device's upstream MAC address, transmitpower level, and configuration number “seriesID”. As indicated earlier,the power level setting 0x01 is selected when the network equipmentcommands the remote device to search for the current power level. Theremote device responds to the CMD_POLL packet with RSP_POLL packet asindicated in step 3 of FIG. 5. Because the transmit power level may notbe correct in the first instance, the response by the remote device maynot be received by the network operator's equipment. For this reason,the network management equipment may issue a repeated CMD_POLL packet asindicated in step 2.

In step four of FIG. 5 the network management system receives theresponse from the remote device and generates a configuration messageCMD_CONF. This is addressed to the remote device's temporary MAC addressbased on the account number assigned to the remote device. The remotedevice decodes the CMD_CONF packet and configures the subscriber IPaddress and the downstream MAC address, and thereafter, switches toreceive packets at the new IP address and MAC address. The networkoperator's equipment follows the CMD_CONF message with a CMD_POLLI orCMD_CREDIT packet which is addressed to the remote device's new IP andMAC addresses, as indicated in step 5. In step 6, a response from theremote device confirms the re-configuration.

When the network management system receives the response poll packet asindicated in FIG. 5, it inspects the seriesID. For new remote devices orremote devices that have lost their configuration, the seriesID is setto zero to inform the network management system of a need forre-configuration. For an established remote device the seriesID is setto the last value received in the CMD_CONF message, and then the networkoperator's equipment determines if re-configuration is required. Toreconfigure the remote device, network operator's equipment implementssteps 4, 5 and 6 of FIG. 5.

Downstream Packet Filtering

The remote device filters packets on the downstream channel using thedestination MAC address of the Ethernet frame. The downstream MACaddress “downMacAddr” is assigned to the remote device by the networkequipment. The IP address of the remote equipment is assigned as part ofan installation scheme and can be changed as requested by the cableoperator. The remote device receives packets that are addressed eitherto its assigned IP address, IP multicast address or IP broadcastaddress. The IP address assigned to the remote device is used as thedestination address on the downstream channel and as the source addressof the upstream channel. The remote device discards packets receivedwith destination MAC addresses not assigned to it. The remote device isprovisioned to prevent risk of listening which cannot be defeated byre-programming or switch settings. An initial default assigned IPaddress can also be assigned to the remote device. The remote devicealso receives packets with an Ethernet broadcast address or assignedmulticast addresses.

Account Management

The network management system is also provided with billing managementfunctions including the ability to keep track of byte counts and packetcounts. Usage information is tracked and collected based on IP sourceand destination addresses. Generally, information collected by thebilling management function of the network management system includes abilling record ID, billing data collecting device ID, date, time, clientID, client IP address and activity records. Monitored account activityincludes upstream/downstream packet counts, upstream/downstream bytecounts, and other activity on the network, including quality of servicecompliance statistics.

In addition, the network management system is provided with accountmanagement functions which permit the network operator to add or deletea client from the database, to modify or reconfigure client information,or to initiate an installation/re-configuration process. Furthermore,the account management function displays the state of remote devices,e.g. whether it is not configured, in test, non-responsive, active,residing on a dedicated or shared channel or idled. The account manageralso displays usage statistics and currently available billing records.The operator may also suspend service to a remote device, as well asdistribute new or upgraded network operating software to remote devices.

Based on the teachings hereof, variations of the disclosed embodimentsare apparent to those skilled in the art. Although a two-way cable andtelephony return cable systems are illustrated, the invention alsoembraces wireless, optical, fiber, satellite broadcast and cellularsystems. Return paths may include telephone, router and RF transmissionlinks, such as point-to-point radio frequency links. Other adaptationsand substitutions of other components and steps are also evident fromthe teachings hereof. Thus, we do not intend to limit our invention towhat is depicted or described, but instead, include all suchadaptations, modifications and substitutions now known or which maybecome known to those skilled in the art.

We claim:
 1. In an asymmetric communication system for effectingcommunications between a server and a plurality of remote processordevices over a high-speed downstream channel and a lower speed upstreamchannel interposed between said server and said remote processordevices, the improvement comprising: an independently operatingdownstream controller for transferring information to said remoteprocessor devices; an independently operating upstream controller forreceiving information from said remote processor devices; aconfiguration manager utilizing each of said upstream and downstreamcontrollers to assign and, by obtaining feedback from said remoteprocessor devices, to confirm assignment of an IP address to a remoteprocessor device based on a detected identification of said remoteprocessor device when connected to and operating on said asymmetriccommunication system; and wherein said upstream controller includesdigital signal processors for analyzing and registering in a memory thequality of upstream transmissions by said remote processor devices. 2.The two-way asymmetric network as recited in claim 1 wherein assignmentof upstream channels to send remote processor devices is made inaccordance with information analyzed by said digital signal processors.3. The two-way asymmetric network as recited in claim 1 wherein saiddownstream controller utilizes quadrature amplitude modulationtechniques for transmitting digital beta signals downstream to saidremote processor devices.
 4. The two-way asymmetric network as recitedin claim 3 wherein said remote processor devices utilizes VSB modulationtechniques for encoding information signals transmitted upstream to saidupstream controller.
 5. The two-way asymmetric network as recited inclaim 1 wherein said remote processor devices includes a processor forreceiving network operating software automatically downloaded fromconfiguration manager.
 6. The two-way asymmetric network as recited inclaim 1 wherein said configuration manager issues control packets thatassign one of shared channel used and dedicated channel use two-wayremote processor device.
 7. The two-way asymmetric network as recited inclaim 1 wherein said configuration manager issues the control packetcontaining information that assigns the class of service level for aremote processor device connected to said network.